Immediately Dangerous to Life or Health Concentrations (IDLH)

Description of substance: Colorless gas with a disagreeable odor like garlic or rotten cabbage.

LEL:. . 3.9% (10% LEL, 3,900 ppm)

Original (SCP) IDLH: 400 ppm

Basis for original (SCP) IDLH: Because no useful data on acute inhalation toxicity are available on which to base the IDLH for methyl mercaptan, the chosen IDLH is based on an analogy with hydrogen sulfide. ACGIH [1971] reported that some investigators show toxicities of the same magnitude for hydrogen sulfide and methyl mercaptan [Ljunggren and Norberg 1943]; others indicate that the toxicity of methyl mercaptan is somewhat less than that of hydrogen sulfide [DeRekowski 1893; Frankel 1921]. Patty [1963] reported that 400 to 700 ppm hydrogen sulfide is dangerous after exposure of 0.5 to 1 hour [Henderson and Haggard 1943]. AIHA [1971] reported that concentrations of 400 to 700 ppm hydrogen sulfide caused loss of consciousness and possible death in 0.5 to 1 hour [MCA 1950]. Based on the data cited above, an IDLH of 400 ppm is chosen.

Short-term exposure guidelines: None developed

ACUTE TOXICITY DATA:

Lethal concentration data:

Species

Reference

LC50 (ppm)

LCLo (ppm)

Time

Adjusted 0.5-hr LC (CF)

Derived value

MouseRat

Seluzhitsky 1972Tansy et al. 1981

3.3675

———-

2 hr4 hr

4 ppm (1.25)1,350 ppm (2.0)

0.4 ppm135 ppm

Lethal dose data:

Species

Reference

Route

LD50 (mg/kg)

LDLo (mg/kg)

Adjusted LD

Derived value

Mammal

Seluzhitsky 1972

?

60.67

—–

212 ppm

21 ppm

Human data: Students accidentally exposed to about 4 ppm for several hours experienced headaches and nausea [Clayton and Clayton 1981]. Some investigators have reported that the toxicity of methyl mercaptan is similar to hydrogen sulfide while others report the toxicity to be somewhat less than hydrogen sulfide [DeRekowski 1893; Frankel 1921].

Revised IDLH: 150 ppmBasis for revised IDLH: The revised IDLH for methyl mercaptan is 150 ppm based on acute inhalation toxicity data in animals [Tansy et al. 1981] and an analogy to hydrogen sulfide [DeRekowski 1893; Frankel 1921] which has a revised IDLH of 150 ppm.

10. Seluzhitsky GV [1972]. Experimental data for substantiation of the threshold of methyl mercaptan, dimethyl sulfide, and dimethyldisulfide in the air of the working zone of paper industries. Gig Tr Prof Zabol 16(6):46-47 (in Russian).